MOSCOW, May 16. /ITAR-TASS/. The satellite launch failure was caused by malfunction of the steering engine unit of the third stage of the Proton-M. It malfunctioned at the 545th second of the flight, a source at the Baikonur space center told ITAR-TASS on Friday.

The Proton with the Express-AM4R communication satellite was launched from Baikonur early on Friday, at 01.42 Moscow time.

A spokesperson for the Russian Federal Space Agency (Roscosmos) confirmed that the satellite was not put into orbit because of malfunction of the third stage of the rocket.

The Roscosmos head's press secretary Irina Zubareva said a state commission was investigating the accident. Members of the commission were analyzing the telemetric information and investigating what caused the malfunction, she said.

A space agency source told ITAR-TASS earlier that the head unit with the Express-AM4R satellite was in orbit and that most the rocket was likely in an unplanned orbit. The failure was not surely to cause its fall, he said.